In recent years, an input unit such as an operation unit, a switch and the like for receiving an input operation by a user, a mobile terminal such as a mobile phone having a touch sensor such as a touch panel, a touch switch and the like has been popularly used. Such a mobile terminal, as illustrated in FIG. 11, for example, may be used under a circumstance where, such as in a train packed with passengers, the user has a physical and mental difficulty in operating as viewing a screen of the mobile terminal. When the user operates the mobile terminal relying on his/her sense without viewing the screen under such a circumstance, since the touch panel has no bumped or dented buttons, the user is likely to operate a wrong key. As a conventional technique, there is a scheme, as a method to dynamically display an operation interface on the touch panel, to display a soft keyboard at a contact position when a contact area of a user's finger contacting a tablet exceeds a threshold (for example, see Patent Document 1).
Patent Document 1: Japanese Patent Laid-Open No. 11-272423